The present general inventive concept relates to a device for conversion of thermodynamic energy into electrical energy.
There is a large variety of ways of generating electric power from mechanical energy of motion involving different efficiencies. In most cases, generators are used which transform a rotary motion. However, such periodically operating machines achieve an acceptable efficiency only as of a specific minimum frequency (rotational speed). When the energy supply is not constant, the conversion of energy is inefficient. A decrease in the supply of energy results in lower rotational speeds which are outside of the optimum operating range of the machine. This is often compensated for by transmissions, which, however, results in a reduction of the overall efficiency and in higher costs. Switching the machine off and on again does not satisfactorily solve this problem because of the associated losses.
A totally different approach for the generation of power from energy of motion is found in the publication: H. Polinder, M. E. C. Damen, F. Gardner, “Design, modeling and test results of the AWS PM linear generator”; in European Transactions on Electrical Power, 2005 (vol. 15), pp. 245-256. In this concept, the pressure originating from ocean waves is converted into mechanical energy of motion and transformed into electric power with the aid of a linear generator. But in this case too, the efficiency is most likely subject to strong fluctuations in particular in the conversion of pressure into motion, due to the non-constant supply of energy. The working cycle of the device is imposed by the natural wave formation and wave motion and can not be varied. In addition, the high demands on the dimensional relationships of the pressure cylinder used and of the linear generator as caused by the dynamic wave motions are assumed to result in a lower total energy transformation efficiency.
A further problem resides in that irregular voltage pulses generated by a linear generator (individual sporadic pulses of different amplitudes and durations) are not suitable for feeding into an electric power grid. Until now, this problem has been solved by first converting the voltage pulses into a direct voltage. For feeding into an electric power grid, this direct voltage is converted into a suitable alternating voltage by a grid-synchronous inverter. These measures, however, turn out to be very involved and are difficult to put to practice on a large scale. In addition, this type of conversion has an adverse effect on the efficiency. An alternative solution provides for the generation of rotational energy from the voltage pulses. A subsequent transformation and inversion of the output voltage results in an alternating voltage suitable for feeding. In this case too, the relatively high expenditure and the inevitable losses are disadvantageous.